Thing is, no matter which way it is, not all the clients are going to be happy. Provide bbfs, some clients aren't happy, don't provide bbfs, some clients aren't going to be happy. But what really ticks off most everyone are the ones who do provide it but say they don't. The guys that don't want to see girls doing bbfs are ticked off when they find out a girl they are seeing does bbfs, guys who want bbfs but don't get it but find out a girl does do it, they are ticked off, the only one happy is the one looking for it and she does it with them. If the girl wants to provide bbfs, provide it, if she doesn't want to provide it, don't. And no matter how quiet you want it to be, it always gets out because guys like to talk.
But whichever way you decide, be aware you cannot make all the people happy, and yes guys are going to ask if that is what they are seeking. Better they ask upfront as everyone knows, you can say no and the client can decide if that is a deal breaker.